1. Field of the Invention
The invention relates to a dilatable cardiac electrode arrangement for implantation in particular in the coronary sinus of the heart.
2. Background Art
As for the background of the invention, it can be said that fundamentally, cardiac pacemakers and defibrillators, by their electrode arrangements, take access to the right ventricle of the heart. On the one hand, this is due to the better accessibility of the right ventricles for corresponding electrode catheters, on the other hand the sinoatrial node tissue as a natural pacemaker of the healthy heart is also located in the right portion of the heart, namely in the area of the right atrium.
The left ventricles are badly accessible for conventional transvenous electrode implantation procedures. Since the stimulation of the myocardium spreads automatically to the other side of the heart, measuring and stimulation via electrode arrangements that are implanted in the right ventricle will as a rule be sufficient.
However, the right ventricles only attend to the pulmonary circulation of smaller volume and are therefore dimensioned smaller than the left ventricles. Consequently, they participate only to a reduced extent in the total heart pumping capacity. Owing to the difference in dimension and importance of the right and the left half of the heart, there is a fundamental interest, from a cardiologic point of view, to have direct access by corresponding electrode arrangements also to the left side of the heart. For instance, the time lapse of stimulus propagation from the right to the left side of the heart can thus be stated. Furthermore, certain forms of tachycardiac arrythmia can be combated by corresponding electrode arrangements on the left side of the heart, such as disorders in which the stimulation of the myocardium passes in a circuit through the left atrium, both ventricles, the right atrium, the left atrium etc. Such tachycardiac arrythmias can be diagnosed at an early stage from the accompanying overlong periods of stimulus conduction between the left and the right atrium.
Typically, the left atrium of the heart andxe2x80x94with certain reservationsxe2x80x94also the left ventricle can be reached by electrode arrangements which are implanted in the coronary sinus on the left side of the heart. To this end, various prior art suggestions have been made.
For instance, a pacemaker electrode is known from U.S. Pat. No. 5,423,772, having three portions of varying rigidity, namely a main reinforced portion, an intermediate zone portion and a soft tip portion. The end of this catheter that can be introduced into the coronary sinus further comprises two curved portions of a greater radius of curvature upstream of the tip and a smaller radius of curvature at the tip. The first curvature provides for the electrode to be fixed mechanically in the coronary sinus, whereas the hooked end improves the angle and the pressure, relative to the wall of the coronary sinus, of a tip electrode disposed on the tip of the catheter.
As regards the number of electrodes and their placement on the body of the catheter, U.S. Pat. No. 5,423,772 illustrates, in addition to the tip electrode, only some further annular electrodes of approximately the same size, the number of which is specified to be ten or more. The number of electrodes and their placement is intended to comply with the respective sensing purposes of the electrode arrangement.
Problems in the implantation of electrode catheters in particular in the coronary sinus reside in that the implanted catheter leads to stenosis of the vessel cross section and thus to a restriction in the flow of blood, which means a considerable drawback in the supply to the heart.
To solve these problems, U.S. Pat. No. 5,170,802 proposes a dilatable electrode arrangement for implantation in particular in the coronary sinus of the heart, in which one or several electrodes are provided, which are expandable in the way of a stent and are coupled to individual conductors or to a common collective conductor. Dilatation of the electrode arrangement may take placexe2x80x94as known from vessel wall supports or xe2x80x9cstentsxe2x80x9dxe2x80x94by a balloon catheter or by a spring design of the electrode structure. In terms of fact, U.S. Pat. No. 5,170,802 discloses a defibrillation electrode.
Finally, U.S. Pat. No. 5,531,779 teaches a defibrillation electrode of the type of a stent, the electrode body of which consists of individual wire filaments which, in the expanded condition, form sort of a closed basket. The ends of these wire filaments are collected by ring or cap type tops of electrically conductive material and thus fixed mechanically. The conductor of the electrode is electrically connected via one of the two caps on the ends.
It is an object of the invention to improve the functionality of dilatable heart electrode arrangements for implantation in particular in the coronary sinus of the heart and in particular to create a combined defibrillator and pacemaker electrode for the coronary sinus.
This object is attained in a dilatable cardiac electrode arrangement for implantation in particular in the coronary sinus of the heart, comprising a defibrillator electrode of the type of a stent having an expandable, electrically conductive structure; pacemaker electrodes in the form of a circle or a section of a circle, which have a smaller surface as compared to the defibrillator electrode, and which are disposed on the ends, facing away from each other, of the defibrillator electrode, and which also have an electrically conductive structure which is expandable in the way of a stent; insulation zones between the pacemaker electrodes on the one hand and the defibrillator electrode on the other; and electric lines for the defibrillator and pacemaker electrodes. Correspondingly, provision is made for a defibrillator electrode of the type of a stent having an expandable and electrically conductive structure on the one hand and for two pacemaker electrodes on the other hand, which have a smaller surface as compared to the defibrillation electrode and are disposed on the ends, facing away from each other, of the defibrillator electrode and also have an electrically conductive structure which is expandable in the way of a stent. Insulation zones are provided between the pacemaker electrodes on the one hand and the defibrillator electrode on the other. They serve for electrically insulating the mentioned electrodes from each other and moreover produce the mechanical connection between the individual electrodes. Finally, electric lines are provided for the defibrillator and pacemaker electrodes. The term xe2x80x9cin the form of a section of a circlexe2x80x9d means a divided annular electrode, in which only peripheral sections serve as a sensing electrode.
As a result of the design, according to the invention, of a cardiac electrode arrangement, electrode implants of combined defibrillator and pacemaker functionality can be inserted also in the area of the left side of the heart at a reasonable implantation expenditure.